Process for treating iron.



W. J. DIEDERICHS. PROCESS FOR TREATING IRON. 'APPLICATION FILED APR. o.`97.

"1,325,626. Pate'nted Dec. 23,1919;

n&

WILLIAM J. DIEDERICHS, OF ITHACA; NEW YORK.

PROCESS'FOR TREATING IRON.

Specification of Letters Patent.

Patented Dec. 23, 1919.

Application filed April' 10. 19l7. Serial No. 161963.

Be it kaown that l. lVILLIAw .T. Drena- RH' S, a citizen ot' the Ynited States residiug at lthaca, iu the county of Tonkins and State ot' New York, have invented certain new and uset'ul luprovenents in Processes for Treating Iron, ot' which the following is a spccification. I

The object ot' this invention is to provide a new' and improved process for treating white cast iron by which an iron' is produced having usually sonewhat greater strength than white cast iron and much greater strength than gray cast iron.

This and other objects of the invention will be described in the specifi'cation and pointed out in the claim at the end thereot'. Drawings have been added t'or'the purpose of showing nore fully how the process may be worked.

In the drawings F igure l is a perspective view of a furnace by which ny process nay be Conveniently worked.

Fig. 2 c is a vertical trausverse section through the turnace illustrated in Fig. 1.

In the drawings like reference nunerals indicate like parts.

In the drawings reference numer'al l indicates the body of the turnace having an opening 2 in the front thereof to close which the hinged door 3 is provided.

Inside of the turnace a charging floor 4 is provided elevated above the main floor 5 of the furnace. Through the sides of the furnace are openings indicated at (3 and 7 through which the conbustible nixture is projected into the furnace under the charging floor by the burning of which conbustible mixture the furnace is heated. The products of conbustion circulate through the furnace and above the chargng floor on which the iron which is being treated 'is held after which the products ot' combustion escapo through the opening S at the top of the furnace.

The furnace illustrated and described herewith is merely an elementary furnace and is shown for convenience and completeness only, it being understood that any type of furnace or heating apparatus-by which the proper degree of temperature can be secured and naintainechso that iron can be exposed to that temperature, may in extensive operation it ivill be desirable to use a furnace that can be i with' the iron and in wh h the iron will` be used, and

charged at one end v nore progressively the t'urnace at a rate that will secure its exposure to the desired temperature for the proper length of time by the tiu'e it energes at. the other end ot' the turnacei and for this purpose any ot' the many well known types ot' t'urnaces nay be used.

lt will he also understood that the furnace may be heated by any of the well known t'uels such as gas, oil, or powdered coal burnt in connection with air and they may be used in such proportions as to secure either an oxidizin a neutral, or a reducing atmosphere in the r'urnace. or the heat may he secured electrically instead or by a cou'bination of conbustion and electricity, or in any other n'anner that may he. desired so long as the proper temperature is Secured.

The iron used in this process is known as white cast iron such as is used in making ualleable castings. Thiswhite cast iron ditfers princi nlly fron\ ordinary gray cast iron in that while both contain carbon the White cast iron contains the carbon wholly or principally in the form of carhid of iron represented by the t'ornula l`eC, while gray cast iron contains the. earbon to a great degree in the t'orn of graphite or graphit'ic carbon.

The process consists in raising the temperature ot' white cast iron with convenient rapidity to about 1,000 degrees centigrade and holding it at that te'perature from about a halt hour to several hours or more and then letting it cool nornally without exposing it to drafts. This can be done best by covering the iron with sand, cement, or lime, or other neutral material. As a result of this treatuent I have found that the tensile strength of the iron is usually more than the tensile strength of the white cast iron from which it is made so that it requires a nuch higher stress to break it. I have also found that the resulting iron possesses other properties that white cast iron does not possess as will presently be explained.

I have also found that the temperature may be varied with satisfactory results between 950 and 1050 degrees centigrade, and thatthe length of exposure to the heat may be varied within considerable limits, it being desirable sometimes to vary the temperature or time or both', according to the composition of the metal, the size and shape of the eastings and the properties desired.

A temperature lower than 950 degrees eentigrade can probably be used with a much toward the other end of longer eXposure and a temperature higher than 1050 degrees centigrade may be used with shorter exposure, but with danger of Warping or melting.

I believe that by this process the carbid of iron of the white cast iron is partially decomposed into iron and carbon, but probably not to the same eXtent that takes place in making commercial malleable castings.

It is well known that ordinarly in making malleable castings the iron is packed with some oxidizing material in sealed cast iron boxes which are loaded into the furnace while the furnace is cold and the furnace is then gradually raised to a temperature of between 800 and 850 degrees centigrade and the furnace is maintained at that temperature for at least siXty hours after which the furance is gradually cooled, the whole process requiring aweek or more of continuous operation. In the making of mallable castings the iron carbid is changed mainly to iron and graphite. The resulting iron has a lower tensile strength than the white cast iron from which it was made, but it will bend or Stretch to an appreciable degree which is not true of the white cast iron.

In working my process I use white cast iron just as is used in making malleable castings, but I use a very different and shorter process and obtain a product that is radically different from malleable castings.

The product of my process dilfers from malleable cast iron in that it has a much higher strength and gives a much better machined or ground surface, but cannot be bent or stretched appreciably before breaking, and because of its increased tensile strength it is much superior to ordinary gray cast iron which it resembles in practically all other respects, such as stiffness, hardness etc. In some respects it can be machined easier machine tools because it dulls the cutting tools very rapidly. Cast iron made by this process is believed to be especially valua ble wherever metal having the properties of gray cast iron, but of higher strength is desired, it having` been shown that while gray cast iron has ordinarily a tensile strength of from 20,000 to 30,000 pounds per square inch and white cast iron has ordinarily a strength of from 45,000 to 50,000 pounds to the square inch, metal produced by this process has been found to have a strength of from 70,000 to 80,000

pounds to the square inch or even higher.

I claim:

The process for the heat treatment of castings from white cast iron which consists in (l) the subjecting of the casting to a heating in the n'eighborhood of 1000 C. for a period ranging from `about thirty minutes to' five hours, (2) the removing of the casting from the furnace after having been subjected to the above heat and the cooling of the casting gradually and uniformly.

In testimony whereof I afiix my signature in the presence 'of two witnesses.

WILLIAM J. DEDERICHS.

VVitnesses:

- ERIO ISGHINGER, EUGENE RAINES. 

